It is sometimes necessary to de-ice certain portions of an aircraft prior to take-off.
Existing technology in common use today involves the spraying of large quantities of chemicals onto the working surfaces (e.g., wings, rudder, ailerons, flaps, stabilizers, etc.) of the aircraft. These chemicals are normally applied just prior to the aircraft's departure from the boarding gate. Federal requirements dictate a maximum time interval between application of the de-icing spray and take-off. This time interval is usually on the order of from about fifteen to about thirty minutes. Unfortunately, with the traffic jams common at some major airports, the departure interval is often extended beyond that recommended. If this occurs, the plane must sometimes be de-iced a second time before take-off. The desire to maintain established schedules and to minimize costs makes this second step undesirable, even if needed. The presence of ice and snow on airfoil surfaces during take-off has been indicated as the probable cause of many crashes.
The foregoing, when considered along with soon-to-be-enforced stricter environmental regulations concerning the handling, storage, use and collection of oversprayed de-icing chemicals, establishes a present need to find a better way to remove accumulations of ice and snow in preparation for take-off.
Two types of de-icing chemicals are in use today. The United States typically uses Type I, which is a mixture of ethylene glycol or propylene glycol and water. This mixture is heated to about 140.degree.-180.degree. F., and then sprayed on the aircraft. European countries commonly use Type II. This is a blend of glycol and a thickening agent, which creates a thicker jelly-like substance. The Type It mixture does hold longer, but can affect take-off of small aircraft. Hence, it is not recommended for use on aircraft having rotation speeds of less than about 85 knots.
It has been proposed that all U.S. airport de-icing equipment be modified to use European Type II chemicals. However this has shortcomings. Upon information and belief, propylene glycol is considered safe to humans by the Food and Drug Administration, but is harmful to the environment. While not currently regulated by OSHA, it has been reported to cause skin irritation, and is listed as a hazardous air pollutant in the Clean Air Act Amendments of 1990. Ethylene glycol is poisonous to humans, and is regulated by OSHA because of a risk of throat and respiratory tract irritation. The Water Quality Act of 1987 prohibits the discharge of polluted water into navigable waters and regulations have been promulgated to prevent airports from dumping or discharging glycol-contaminated storm water run-off into rivers and sewer systems.
Accordingly, there is believed to be a clear and present need for an improved method of, and apparatus for, de-icing portions of an aircraft without the need of such de-icing chemicals.